listen to Rep Wesley Hunt's opening statement about reforming birthright citizenship.
Congressman Wesley Hunt Ignites Debate at Birthright Citizenship Hearing! - YouTube

He makes it clear that the 14th amendment was intended to make former slaves and their children American citizens .

This whole notion of a birthright citizenship is against the whole founding principle. Free people are not bound to citizenship by birth. We renounced that feudal notion with the Declaration of Independence.

The intent of the clause language 'subject to the complete jurisdiction of the United States” is willfully misinterpreted . Senator Jacob Howard who authored the clause made it clear when arguing for passage that native Americans ;who were born within the geographic United States and subject to the jurisdiction were not eligible because the intent of it was "allegiance " Their allegiance was to their tribe . He went on to add that it not only excludes Native Americans. The exact quote is .....

This amendment which I have offered is simply declaratory of what I regard as the law of the land already, that every person born within the limits of the United States and subject to their jurisdiction, is by virtue of natural law and national law a citizen of the United States. This will not, of course, include persons born in the United States who are foreigners, aliens, who belong to the families of ambassadors or foreign ministers accredited to the Government of the United States, but will include every other class of persons.

The reason this was necessary was to constitutionally reverse the Dredd Scott decision wrongfully decided by the Roger Taney SCOTUS declaring that Blacks and their descendants could never be citizens .

Native Americans were later granted the right under an act of Congress in 1924.
Indian Citizenship Act of 1924 - Immigration History

This set a precedent that Congress could use today to define who is eligible .